Even with front-line centerpiece Ike Opara back home in Minnesota rehabbing, Minnesota United reached the MLS is Back Tournament quarterfinal against San Jose on Saturday primarily with its precision to convert set pieces at which Opara so excels.

The Loons have scored three of their five goals in four tournament games using set pieces, in which players position themselves to receive the ball from a restart in play after a foul or the ball bounding out of play. That could be off corner kicks, crosses or direct shots from a free kick, including penalties.

Two of those three set-piece goals came on a corner kick, the other on a free kick near the left sideline. They have allowed one goal on opponents’ set pieces, a game-tying half-volley strike by Colorado’s Jonathan Lewis in a 2-2 group-play draw.

“The second goal, we should do better with that one and maybe we’d win,” Loons midfielder Jan Gregus said. “But I don’t know.”

All three goals the Loons have scored on set pieces started at the same place: the foot of their designated free-kick specialist, Gregus.

“It starts with the great service that Jan has been able to put into for our attacking players,” Loons goalkeeper Tyler Miller said in a video conference call. “Any players in that situation, it really stems from the quality of the service, and Jan has been able to deliver so far in this tournament.”

Gregus’ service has produced all three goals, in different ways. His floating, curved free kick from well outside the 18-yard box went off Sporting Kansas City winger Khiry Shelton’s chest for an own goal that was the first of two second-half stoppage time goals in a 2-1 comeback victory in the tournament opener.

Midfielder Ethan Finlay’s toe-flick on Gregus’ low driving free kick from the left side was the Loons’ first goal in that 2-2 tie with Colorado. Then Robin Lod both started with a header and finished with an off-foot volley of a Gregus corner kick for the team’s only goal in Tuesday’s 1-1 knockout-round draw with Columbus. The Loons went on to win in a penalty-kick shootout.

“Set pieces and good finishers,” Gregus said on a video call. “My job is just put it in the right spot and if they finish it with a goal, good for us.”

Even with 6-2 Opara missing, Loons coach Adrian Heath notes the height his team still has for set pieces at either end: 6-3 defender Jose Aja, 6-2 defender Michael Boxall and, later in games, 6-4 striker Aaron Schoenfeld.

Opara scored twice on headers off corner kicks in the Loons’ 5-2 victory at San Jose in March, in the season’s second week.

“Ultimately, it’s the service,” Heath said. “If we can get it in the right spots, we do have people — guys like Boxy and Jose Aja — who can attack the ball. Luis [Amarilla] has good movement. Obviously, we miss the threat of Ike. We’ll obviously miss that.”